The liquid penetrant testing in ASME standards refers to the ASME Code Section V Article 6, and it addresses the different methods and technique and corresponding requirements.
The requirements include to the cleaning methods, penetrant dwell time, developer dwell time, liquid penetrant material specification, test object temperature requirements, technicians qualification requirements, test procedure content requirements, test report requirements, etc.
The article 6 of ASME Code does not provide acceptance criteria to evaluate test result. The construction code cover that section.
For example, if the test object is a component from power boiler, then the acceptance criteria can be found in ASME Code Section I or if the test object is a part of the pressure vessel, then acceptance criteria can be found in the ASME VIII Div 1 Appendix 8.
The article 6 of ASME Code Section V introduces two techniques with the total of 6 processes as followings:
Each of above-mentioned technique can be applied with one of the following methods
For instance, based on written procedure (test procedure) you may perform the test with color contrast technique and with the removable solvent method. So totally you have six types of liquid penetrant testing.
Obviously, the fluorescent technique has more sensitivity than color contrast technique. You may be able to detect a defect by fluorescent technique but not with color contrast technique.
In general, the written practice (the test procedure) shall be approved by certified ASNT Level III specialist and be conducted by Level II. The test result can be evaluated/interpreted based on the acceptance criteria either by Level II or Level III.
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